Ok- after looking at the aftermarket tube rebuilds (with incorrect bearing clearances- C3 v C4-correct one) and looking at my tube with 165k miles on it, I decided to make my own tube, and since I started with a sorta clean slate, I opted for aluminum over steel. Engineering is done, assembly (welding parts) will commence on Monday. The aluminum tube is lighter, (I'll weigh both and post results), can be set up for any number of bearings, uses the correct clearance (C4) and is rebuildable by the average DIY type. If you can remove your own tube, you can rebuild this tube. All bolts and screws are safety wired for security. Testing will commence as soon as either A) I get a willing subject or B) I put it in my 951. Since I don't flog my 951 much <img border="0" alt="[hiha]" title="" src="graemlins/roflmao.gif" /> I would rather put it in a track car. If this works out ok, I'll be making more, including early 924 tubes as well. Future options under consideration- different driveshaft materials (titanium, carbon) and further techniques to lose more weight. Can't resist tinkering.

 

Dave, what is the estimate on cost? If you can get close to the cost or a rebuild, you should be able to sell a LOT of them.

 

Not sure, will have a better handle on it if I can get materials in quantity. The prototype is usually the most expensive but if there is a real interest in shedding weight and getting a good tube, it won't be much more than the rebuild from others.

 

Hm-m-m, Keep the info coming. I've got a TT rebuild in my future and your idea is very logical.

 

What is the rebound rate on aluminum? Most metal has a rebound ability? I thought that aluminum once bent is bent? I am probably wrong. but would like to know this.

 

I think it depends on how the alum is annealed. The harder the aluminum generally mean the more brittle meaning the higher the ultimate strength, the less the bending before breaking. I think a bit of engineering will be involved to determine the thickness required to handle the torque from engine to transmission without deforming or cracking the metal. Personally, I think it will work with a relative hard alloy aluminum unless it breaks from severe abuse. Motorcycle frames are pretty tough and if the tube is made of the same alloy I believe this will be a new innovation we need for the 944/951. Keep on tinkering and keep us updated.

 

Alloy being used is 6061-T6 in 3.5 dia with 1/4in wall thickness. Thus far, we think it will be far in excess strengthwise of what is required. From my calculations, it will meet the existing tube. I'm having someone else check the numbers to verify the finger math. We should have a test prototype completed this week.

 

My guess is that it will last a lot longer than the ring & pinion gear will...

 

Scootin - I laughed, I cried... <img border="0" alt="[hiha]" title="" src="graemlins/roflmao.gif" /> <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" />

FWIW, There's already a carbon fiber replacment for the torque tube / drive shaft. In the archives...

Skip

 

I always thought this would be a good project, looks like you beat us all to it.

Another idea I had was to use a plasma cutter and remove much of the tube material and then cover with plastic or rubber to seal it back up. This would reduce weight, and no doubt the steel torque tube is way stronger than needed for torque reaction from the engine.

Keep us posted.

Art

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by art:
<strong>I always thought this would be a good project, looks like you beat us all to it.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Porsche beat him to it.

The 937 had an aluminum torque tube!

(That's 924 Carrera GT, yano?)

 

Skip-
Huntley was working on it. No longer on the website I'm told, why?

 

There are lots of different aluminum alloys, god knows I've heard about them from my uncle who used to manage Alcan plants.

I'd get a specialists opinion (metalurgist?) on what would work in this application before going too far. Just my 2 cents.

And, oh yeah, as a Canadian, I can tell you that an aluminum toque would be damn uncomfortable to wear, as well as cold!

 

sounds like the lighter aluminum might be a good way to subtract drivetrain losses and help the engine rev faster. i just have one question: what will the effect of the expansion of aluminum have on the bearings when heated up? do you size everything so that it fits well when cold or when hot?

 

We can build carbon/kevlar tubes but they are expensive at $2500 a pop. For some reason the demand just was not out there? The shaft remains steel just the outer tourqe tube is changed.